Revert "Retire unmaintained CMakeLists.txt."

It turned out that there're some special cases not (yet) covered by the
Makefile. Crossbuilding in specialized chroot environments are one
example.

CMakeLists.txt

@@ -0,0 +1,73 @@
+cmake_minimum_required(VERSION 3.0)
+
+# Enforce "Debug" as standard build type
+if(NOT CMAKE_BUILD_TYPE)
+	set(CMAKE_BUILD_TYPE "Debug" CACHE STRING "Choose the type of build, options are: Debug Release RelWithDebInfo MinSizeRel." FORCE)
+endif(NOT CMAKE_BUILD_TYPE)
+
+# CMake project configuration
+project(yquake2-ctf)
+
+# Enforce compiler flags (GCC / Clang compatible, yquake2
+# won't build with another compiler anyways)
+#  -Wall                -> More warnings
+#  -fno-strict-aliasing -> Quake 2 is far away from strict aliasing
+#  -fwrapv              -> Make signed integer overflows defined
+set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wall -fno-strict-aliasing -fwrapv")
+
+# Use -O2 as maximum optimization level. -O3 has it's problems with yquake2.
+string(REPLACE "-O3" "-O2" CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE}")
+
+# Linker Flags
+if(${CMAKE_SYSTEM_NAME} MATCHES "Windows")
+	list(APPEND CtfLinkerFlags "-lm")
+else()
+	list(APPEND CtfLinkerFlags "-lm -rdynamic")
+endif()
+
+set(Ctf-Source
+	src/menu/menu.c
+	src/monster/move.c
+	src/player/client.c
+	src/player/hud.c
+	src/player/trail.c
+	src/player/view.c
+	src/player/weapon.c
+	src/shared/shared.c
+	src/g_ai.c
+	src/g_chase.c
+	src/g_cmds.c
+	src/g_combat.c
+	src/g_ctf.c
+	src/g_func.c
+	src/g_items.c
+	src/g_main.c
+	src/g_misc.c
+	src/g_monster.c
+	src/g_phys.c
+	src/g_save.c
+	src/g_spawn.c
+	src/g_svcmds.c
+	src/g_target.c
+	src/g_trigger.c
+	src/g_utils.c
+	src/g_weapon.c
+	)
+
+set(Ctf-Header
+	src/header/ctf.h
+	src/header/game.h
+	src/header/local.h
+	src/header/menu.h
+	src/header/shared.h
+	src/monster/player.h
+	)
+
+# Build the ctf dynamic library
+add_library(game SHARED ${Ctf-Source} ${Ctf-Header})
+set_target_properties(game PROPERTIES
+	PREFIX ""
+	LIBRARY_OUTPUT_DIRECTORY_DEBUG ${CMAKE_BINARY_DIR}/Debug
+	LIBRARY_OUTPUT_DIRECTORY_RELEASE ${CMAKE_BINARY_DIR}/Release
+)
+target_link_libraries(game ${CtfLinkerFlags})